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Read Me: Best Way to Resolve Loops Context? Alias?
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rajchowdary81
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PostPosted: Mon May 07, 2007 9:50 am 
Post subject: Read Me: Best Way to Resolve Loops Context? Alias?

Hi all,

I am new to Business Objects , and a FAQ in BO is which is the best way to resolve loops , SO Guys can anyone clarify me ...which is the best way , Aliases or Contexts..

Thank you,
Chowdary

[Edited title and made sticky - Dave Rathbun]
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Namlemez
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PostPosted: Mon May 07, 2007 10:30 am 
Post subject: Re: Best Way to Resolve Loops ....

The best way is whichever way solves your problem icon_smile.gif I use both depending on the situation. If you have a specific problem, try giving us a simple example.
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Steve Krandel
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PostPosted: Mon May 07, 2007 10:51 am 
Post subject: Re: Best Way to Resolve Loops ....

Start by reading the FAQs here on BOB.

As mentioned, there is no "best" way. There is however, a "right" way.

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Mark P
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PostPosted: Tue May 08, 2007 3:49 am 
Post subject: Re: Best Way to Resolve Loops ....

There are two key rules of thumb:
A context for each fact table
An alias for each different use of a reference table - e.g. multiple uses of calendar_ref for invoice dates, sales dates, delivery dates, etc.

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Omkar Paranjpe
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PostPosted: Tue May 08, 2007 11:14 pm 
Post subject: Re: Best Way to Resolve Loops ....

Hi,
Apart from points mentioned by Mark, one other rule. Look at the maintainance point of view also.
I mean if the universe is very large and complex then always try to use contexts. It will reduce the pain of adding redundant aliases.
If universe is a small relatively simple in terms of tables present, joins and other properties of the universe then you can think of aliases.

In my case we have used contexts for derived, complex universe where as aliases in the smaller/simpler one where tables,joins were limited in number.

If your requirements are such that it makes you add aliases regularly then it may cause problem in future as there will redundant aliases in the universe.

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Dave Rathbun
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PostPosted: Wed May 09, 2007 12:08 am 
Post subject: Re: Best Way to Resolve Loops ....

I submit that maintenance doesn't have anything to do with it either. icon_smile.gif

Contexts have a purpose. Aliases have a purpose. In every case I can think of, which one you select is based on the problem you are trying to solve, not really what you think will be the best maintenance option. If you need a context, then you need a context.

The only real alternative to creating contexts is to create more than one universe. That's essentially what a context is, really, by identifying a set of joins that work together you are essentially subdividing a single universe into smaller sub-universes of tables that work together. You could separate them into different universes.

Aliases are not substitutes for contexts, and vice versa. Once you have identified the problem, the solution choice is made for you.

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Mark P
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PostPosted: Wed May 09, 2007 2:44 am 
Post subject: Re: Best Way to Resolve Loops ....

I concur with Dave.

There's no easy way to maintain a wrongly designed universe.

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PostPosted: Wed May 09, 2007 8:49 am 
Post subject: Re: Best Way to Resolve Loops ....

Time for some reading....

http://f1.pg.briefcase.yahoo.com/bc/skrandel@sbcglobal.net/lst?.dir=/Business+Objects&.order=&.view=l&.src=bc&.done=http%3a//f1.pg.briefcase.yahoo.com/

It's in the 2003 or 2004 materials. Yes, I know that seems old, but it hasn't changed.

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Carina
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PostPosted: Fri May 11, 2007 3:20 pm 
Post subject: Re: Best Way to Resolve Loops ....

rajchowdary81 wrote:
Hi all,

I am new to Business Objects , and a FAQ in BO is which is the best way to resolve loops , SO Guys can anyone clarify me ...which is the best way , Aliases or Contexts..

Hi,

I think that the following link may be useful for you: {url=http://support.businessobjects.com/documentation/installation_resources/5i/tips_and_tricks/pdf/universe_design/ut001.pdf]see here[/url]

Good Luck icon_lol.gif
BR, Carina
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Dave Rathbun
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PostPosted: Fri May 11, 2007 4:35 pm 
Post subject: Re: Read Me: Best Way to Resolve Loops

I edited the first post, altered the title, and made this a "Sticky" topic to increase its visibility.
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koilada
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PostPosted: Fri May 11, 2007 4:38 pm 
Post subject: Re: Best Way to Resolve Loops ....

Hi Raj Alias and context are to be used depending upon the loop you encounter. Do let us know if you are struck anywhere in resolving the loops. The best way of designing a universe is keep you Logical Data Model with you and go accordingly.
I feel the best way of designing a universe is inserting one fact table at a time.

1. Insert one fact table and related dimension tables to that fact table.
2. Create all the joins.
3. Check for loops.
4. See if it can be resolved with an alias.
5. Create context. Make sure a context doesnt have any loops
6. Each join must present in atleast one context.

Hope this helps.

Regards
Sridhar
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Dave Rathbun
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PostPosted: Fri May 11, 2007 4:39 pm 
Post subject: Re: Read Me: Best Way to Resolve Loops Context? Alias?

Another reference that contains information on fan traps, chasm traps, and so on, and how to use aliases and/or contexts to resolve them:

http://www.integrasolutions.net/library_presentations.htm#design

There are a number of presentations on that page that will help.

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Dave Rathbun
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PostPosted: Fri May 11, 2007 4:42 pm 
Post subject: Re: Best Way to Resolve Loops ....

koilada wrote:
Alias and context are to be used depending upon the loop you encounter.

Keep in mind that there are context issues in a universe that are not related to loops... a fan or chasm trap does not always include a loop, yet they require contexts, aliases, or a combination to solve.

A chasm trap is a many - one - many chain of tables. You need to use contexts to separate the two ends of that chain, as you cannot get a valid answer by using all three at the same time.

A fan trap is a one - many - many relationship with measures at all levels. You must separate out the measures from the dimension tables using aliases, then use contexts to resolve the resulting chasm traps.

Neither of those situations include loops. icon_smile.gif

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Anita Craig
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PostPosted: Fri May 11, 2007 6:17 pm 
Post subject: Re: Best Way to Resolve Loops ....

And more detailed info on solved fan traps and chasm traps can be found here in our Designer FAQ.
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rajchowdary81
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PostPosted: Thu May 17, 2007 2:05 pm 
Post subject: Re: Best Way to Resolve Loops ....

Thank you all for helping me , I have another doubt , Is there any other purpose of setting cardinalities other than for resolving loops. Does the setting of cardinalities effect the report?

Thank you,
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